Reflective Stack Backlight for Uniform LCD Illumination
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Solution Overview
Problem
Liquid crystal display (LCD) devices face challenges with non-uniform illumination due to spatial separation between light sources and the LCD panel, leading to inefficiencies in light extraction and potential hotspots.
Innovation Solution
Incorporating a reflective stack and a recycling stack in the backlight, which provides a folded beam path for light emission, diffuses light, and recycles untransmitted light to improve uniformity and efficiency of illumination, while maintaining a thin profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional backlight with spatially separated LEDs is used, then the backlight structure is simple, but the illumination uniformity deteriorates causing hotspots and non-uniformity
Solution Approach 1:
A reflective stack is introduced as an intermediary optical element between the light sources and LCD panel. This reflective stack with folded beam path redirects and diffuses light to achieve uniform illumination across the panel, resolving the non-uniformity issue without requiring complex LED arrangements
Solution Approach 2:
The patent transforms the light propagation from a direct linear path to a folded beam path through multiple reflections. This dimensional change in light trajectory allows for better light distribution and uniformity while maintaining a compact backlight structure
2Use of energy by moving object
If light sources are spatially separated from the LCD panel, then the backlight thickness is reduced, but light extraction efficiency deteriorates
Solution Approach 1:
The recycling stack implements continuous light recycling by capturing and redirecting light that would otherwise be lost. This ensures continuous useful action of light extraction, maximizing efficiency while maintaining thin backlight design
Solution Approach 2:
The patent recovers light that would normally be discarded or lost in conventional backlights. The recycling stack captures unused light and redirects it through the LCD panel, improving overall light extraction efficiency without increasing thickness
3Illumination intensity
If a folded beam path is implemented with a reflective stack, then light diffusion and uniformity are improved, but the device complexity increases
Solution Approach 1:
The reflective stack serves multiple functions simultaneously: it creates the folded beam path for light diffusion, acts as a recycling element for unused light, and provides structural support. This multi-functionality reduces the need for separate optical components, managing complexity while achieving excellent light diffusion
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances light diffusion and uniformity across the LCD panel, reducing hotspots and improving light extraction efficiency without increasing the backlight's thickness, resulting in improved display performance.
Implementation Method 1
The reflective stack reflects a portion of the light received from the light sources
Implementation Method 2
a recycling stack that reflects the light from the reflective stack back towards the reflective stack and along the folded beam path
Implementation Method 3
The reflective stack outputs linearly polarized light aligned along a polarization axis of a LCD input polarizer of the LCD panel
Data Source
AI summary
A liquid crystal display (LCD) device including an LCD panel and a backlight. The backlight includes a plurality of light sources to emit light, and a reflective stack. The reflective stack is positioned to receive light emitted from the light sources and transmit the light to the LCD panel. The reflective stack includes optical elements providing a folded beam path for the light emitted from the light sources to the LCD panel. The light emitted from the light sources is diffused while propagating towards and away from the LCD panel along the folded beam path. The folded beam path has an optical distance that is longer than the spatial distance between the light sources and the LCD panel to improve light diffusion by the backlight without substantially increasing backlight thickness.